The present invention generally relates to a ferroelectric device for using the polarization inversion of a ferroelectric such as ferroelectric memory or the like, and more particularly, to a capacitor for relieving distortion stress on the surface so as to improve the characteristics.
Conventionally in this type of capacitor, F.C.C. metal (mainly Pt) is often used as a conductive electrode 2 so as to improve the crystal orientation property of the ferroelectric 2 as shown in FIG. 1. Although it is proposed to form Ta.sub.2 O.sub.5, for example, between a PZT and an electrode, a dielectric constant is still small in the Ta.sub.2 O.sub.5 (.epsilon.r.apprxeq.25) and the inversion voltage becomes high. Further, the crystal property is completely different form the PZT, with a disadvantage that the crystal property becomes worse.
Film fatigue by the polarization inversion in the conventional art is considered to be caused mainly by the orientation properly of the film. It is recently announced that the film fatigue is not solved if the orientation property is improved.
As the ferroelectric (PZT or the like) of a perovskite type cause displacement polarization, the distortion is caused on the surface between what do not cause the displacement polarization such as Pt and so on. The grid breakdown and so on are caused on the surface, because of distortion, into the film fatigue. The present invention relieves the distortion on the surface to be caused on such conventional capacitor as described hereinabove so as to reduce the film fatigue.